i.e. \(\hat{s}\)  and \(\hat{u}\)  are of order of \(Q^2\) . The behavior of the various contributions to the subprocess
amplitudes for \(\hat{t}\rightarrow 0\)  are compiled in Tab. REF . One sees from that table that
the asymptotically dominant contribution comes from longitudinally polarized photons at the twist-2 level.
In fact, the \(\hat{t}\rightarrow 0\)  limit
of (REF ) is the familiar LO, leading-twist result [1]}. On the other hand,
the transverse leading-twist amplitude vanishes proportional to \(\sqrt{-\hat{t}}\)  and, compared to the
longitudinal amplitude, is suppressed by \(1/Q\) . Table REF  also reveals that all twist-3
contributions for longitudinally polarized photons vanish \(\sim \sqrt{-\hat{t}}\)  as a consequence of angular
momentum conservation. The twist-3 contributions for transversely polarized photons remain finite for \(\hat{t}=0\) 
but are suppressed by \(\mu _\pi /Q\)  or \(f_{3\pi }/Q\)  compared to the dominant twist-2 contribution for longitudinally
polarized photons.
<TABLE>